To the Editor:—
I read with interest the study by Tsen et al. 1alleging a faster rate of cervical dilation in parturients receiving a combined spinal–epidural (CSE) analgesia in comparison to conventional epidural analgesia (2.3 ± 2.6 vs. 1.3 ± 0.71 cm/h). First-stage full cervical dilation was shortened by a mean of 78 min in the CSE group. There appear to be subtle differences between the two randomized groups. The CSE group had a lower rate of cervical dilation (2.4 ± 1.4 vs. 2.8 ± 1.4 h). Of the CSE group, 64% had initiation of Pitocin (Fujisawa, Deerfield, IL) before analgesic intervention, in contrast to only 54% of the epidural group. Finally, membranes were ruptured for 7.5 ± 5.6 h before initiation of analgesia in the CSE group but only for 5.9 ± 6.0 h in the epidural group. More frequent observed cervical examinations in one group can lead to a faster observed rate of cervical dilation. Also, oxytocin and ruptured membranes are factors that can promote a faster and more active labor. Although none of the differences were thought to be statistically significant, I believe that the faster first-stage labor may have been a result of a synergistic effect of the three different (but nonstatistically significant) variables, rather than from the type of analgesia. The authors were not troubled by the lack of regularly timed intervals for cervical examinations. I believe differently. The stage was set for the CSE group to have more active and rapid labor, leading to more frequent cervical examinations, resulting in an observational bias of faster cervical dilation. I believe that the two study groups were not optimally balanced, and a multivariate method (e.g. , analysis of covariance) should have been performed.
This study may be misleading to our obstetric colleagues and patients. There may be a false impression that a patient’s labor was prolonged because the anesthesiologist performed a “plain epidural” and not a “walking epidural.” Finally, the authors neglected to address the potential risks and complications of a CSE technique. These include dural puncture, fetal bradycardia, and the lack of a tested epidural catheter. I believe further studies are warranted before conclusions can be made regarding the superiority of a combined regional technique for labor analgesia.